The continuing trend toward high density circuitry has initiated the evolution of printed circuit board connectors which permit electrical communication between a system of bus boards or which transfer power to a mother board from a daughter board. In response to the need for compact circuit elements, connectors with multi-contact capabilities have been fabricated. These multi-contact connectors are generally bussed together to achieve high current carrying capabilities. Although such connectors facilitate board/board power distribution, all bussed connections must be reliable and exact and, thus, are time consuming to assemble and subject to assembly defects. Moreover, maintenance of the multi-contact connectors have proven laborious and costly.
As an alternative to multi-contact connectors, hard wiring methods have been employed which involve soldering, or otherwise mechanically attaching, discrete wires to current carrying devices mounted on printed circuit boards. However, again such systems are labor intensive to assemble and have the significant drawback of poor field serviceability.
In the recent past, attempts have been made to alleviate the problems associated with bussed contacts and discrete wiring. One such attempt included a system of printed circuit board connectors, as disclosed in U.S. Pat. No. 4,749,357 to Foley, which permitted various board/board interplanar relationships without requiring the labor intensive assembly process found in prior art power distribution systems. This system of printed circuit board connectors utilized interchangeable parts so that varied printed circuit board arrangements could be constructed. These circuit board connectors generally included a bus element and an electrical mating contact supported by an integrally attached insulating block, and male and female connectors were recognized in this design. Though the configuration of the printed circuit board connectors met variable design applications, the connectors were fabricated and assembled from a substantial number of different parts, which reduced the cost-effectiveness of the system somewhat.
In an effort to reduce fabrication costs, an improvement was made in the above-described modular connector system. The improved connectors, which had a smaller number of parts, were designed to increase flexibility in the number of possible board/board configurations, as disclosed in U.S. Pat. No. 4,824,380 to Matthews. These more recent modular connectors generally included an insulative housing and a conductive element inserted within the housing. During fabrication, the conductive member was stamped from a sheet of flat metal stock and then bent into shape on a suitable mandrel. The housing was then press fit to the conductive member. The housing included an integrally attached, insulative arm which permitted a common conductor element to extend between adjacent connectors without possible inadvertent contact with other circuit elements.
Though such modular connectors included male and female-type connector elements and permitted chains of circuit boards to be interconnected, precise placement and alignment of the connectors were necessary for proper electrical communication. Further, a more time-efficient method of assembling the housing to the conductive member was desired. Thus, the need for development of a design to further ease connector assembly and to increase connector utility in transferring power from board to board arose.
In conventional printed board circuitry, electrical communication between a series of boards, such as between a mother board and a daughter board, has also been realized by matingly engaging an electrically conductive pin mounted on one board with a compatible socket mounted on a second board. Current practice involves securely fastening the conductive pin to the circuit board by a nut and bolt assembly. This arrangement maintains the conductive pin in a rigid perpendicular posture with respect to the circuit board, resulting in a relatively inflexible engagement between the pin and the socket.
Generally, this type of mating engagement is applied to a mother board-daughter board configuration. Though the pin-socket engagement proves functional under ideal physical conditions, in practice manufacturing tolerances and thermal stresses play an important role in maintaining the integrity of the connection. Circuit board thicknesses may vary due to manufacturing limitations, and, consequently, the printed circuit boards may have different structural responses to expansion and contraction. Any variance in thermal response may realign the boards in a new dimensional configuration, causing weakening of the connection between the conductive pin and the socket. Thus, the conventional method of securing a conductive pin in a rigid posture to a circuit board is not sufficiently compliant to withstand relative movement due to thermal and mechanical forces.
The difficulties suggested in the preceding are not intended to be exhaustive but rather are among many which may tend to reduce the effectiveness of current printed circuit board connector assemblies. Other noteworthy problems may also exist; however, those presented above should be sufficient to demonstrate that printed circuit board assemblies appearing in the past will admit to worthwhile improvement.
Accordingly it is a general object of the invention to provide a printed circuit board assembly which will obviate or minimize difficulties of the type previously described.
It is a specific object of the invention to provide a printed circuit board assembly which will permit a variety of board-board interplanar relationships.
It is another object of the invention to provide a printed circuit board assembly which will accommodate relative misalignment and repositioning of printed circuit boards due to thermal and mechanical stresses.
It is yet another object of the present invention to provide an electrical connector for a printed circuit board assembly which is economical to fabricate and is modular for rapid assembly and mounting of male and female, as well as horizontally and vertically oriented, connectors to printed circuit boards.
It is still another object of the invention to provide a printed circuit board assembly which permits variance in printed circuit board thickness.
It is a further object of the invention to provide a printed circuit board assembly which provides auxiliary contact between connectors to facilitate the transfer of power between a series of circuit boards.
It is still a further object of the invention to provide an electrical connector for a printed circuit board assembly which maximizes the current transfer between a printed circuit board and the electrical connector.
It is yet another object of the invention to provide an electrical connector for a printed circuit board assembly which reduces the possibility of inadvertent electrical communication between adjacent circuit elements.
It is still another object of the invention to provide a printed circuit board assembly which is economical to manufacture, is durable, has a minimum number of parts, and may be easily assembled and cleaned.
It is yet still another object of the invention to provide a printed circuit board assembly which is easily maintained and serviced.